In recent years, various electronic products are developing continuously towards the direction of friendly operations, small sizes, and large displays. In particular, portable electronic products are especially demanding for their volume and display size. Thereby, many electronic products integrates touch panel and LCD panel for eliminating keyboard or saving the space required for operating keys, and thus extending the usable area of displays.
Depending on their sensing principles, general touch panels can be classified into resistive, capacitive, infrared, and ultrasonic types. Thanks to their dust and scrape resistant properties as well as the advantage of high resolution, capacitive touch panels are adopted increasingly in electronic devices.
The principle of a capacitive touch panel is mainly to plate the surface of a glass substrate with a layer of transparent conductive thin film, such as indium-tin oxides, as the sensing structure. When a user touches the panel using his finger, the proximity of the finger changes the coupling capacitance of the sensing structure. The capacitive touch panel can analyze changes in capacitance of the sensing structure and thus determining the touch location of the finger.
FIG. 1 shows a schematic diagram of the electrode structure of a projected capacitive touch sensor according to the prior art. As shown in the figure, the projected capacitive touch sensor adopts two electrode layers to fabricate the electrodes for facilitating scanning of the circuit. The electrode structure according to the prior art mainly comprises a substrate (not shown in the figure), a Y-axis electrode layer 20′, and an X-axis electrode layer 10′. The substrate, for example, is a glass substrate. The Y-axis electrode layer 20′ is disposed on the top surface of the glass substrate, and has multiple Y-axis electrodes (y1, y2, y3, y4 . . .) spaced by a fixed spacing. The X-axis electrode layer 10′ is disposed on the bottom surface of the glass substrate, and has multiple X-axis electrodes (x1, x2, x3, x4 . . .) spaced by a fixed spacing and perpendicular to the Y-axis electrodes. Thereby, when a finger touches or approaches the glass substrate, the capacitance of the X- and Y-axis electrodes at the touched location changes. By using a detecting circuit, the X- and Y-axis coordinate data can be detected.
For using this dual-layer capacitive touch sensor, it is required to dispose X- and Y-axis electrodes on the top and bottom surfaces of the glass substrate, respectively. In general, indium-tin oxides are used for fabricating transparent electrodes, which makes the manufacturing cost high. For solving the problem of the dual-layer capacitive touch sensor, a single-layer capacitive touch sensor is developed. Nonetheless, current single-layer capacitive touch sensor still needs to be improved in multi-touch applications.
Accordingly, the present invention provides a novel sensing structure of touch panel, which can give the touched location on the touch panel accurately without increasing wires. In addition, the area of the touch panel is also reduced.